Process of making sodium-aluminum fluorid.



. STATES PATENT onmoE,

No Drawing.

' T all whomii may 2mm."

GERMANY, ASSIGNOR 0F 0NE-HALF '10 ALEX. HUMANN,

OF DOHNA, GERMANY.

PnocEss or MAKING SODIUM-ALUMINUM FLUORID.

Be it'known that I, EM n TnIsLnn, a subject of the Emperorof Germany, residing at Dohna. in the bezirk of Dresden and Knigdom of Saxony, Germany, have invented certain new and useful Improvements in Processes of Making SodiumsAluminum Fluorid; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a' process of making sodium-aluminuii1 fluorid,- and has-for its object to render the process moreexpe,

ditious and less expensive.

soda,alumina and hydrofluoric acid to act on. each other in stoechiometric proportions,

, which causes this double salt to separate out sition.

in'a very difficulty soluble form. It has also been produced by substituting silico-fluoric (hydrofluosilicic) acid for fiuoric acid. Instead of obtaining the fiuorin necessary for this process from the hydro-fluorio acid or hydro-silico-fluoric acid, it has been found that the fluorin present in sodium silicofluorid which is a cheap by-product of the manufacture ofsuper-phosphates, which can be conveniently and completely united with alumina and soda, in which case, .it is true,

he pure sodium aluminum. fluorid results, but a preparation mixed with silicic acid in finely divided form is produced, which, however, although so mixed is found to be useful in the ceramic industry, for the preparation of milk-glass and enamel, as silica forms a large proportion of glasses and enamels.

It is known that soluble, fluosilicic compounds and alkali silico fluorids on digesting with alkalis undergo decomposition into alkali fluorids and silicic acid. Previous experiences, however, disclose the fact that this decomposition is incomplete, as the gelatinous silicic acid therein formed acts as a hindrance to prevent complete decompo- (German patent to Reich, 96,226 corresponding to British patent to Reich, 21073 of 1897.) Therefore, if it is wished to convert alkali silico-fluoride completely into alkali fluorids, the higher temperature of an incandescent process must be used. (Rick- Specification of Letters Patent;

. mar-m and Rappe, German Patent l10250.)

Patented Jan."16,1e12. Application filed January 27, 1910. Serial No. 540,434.

Furthermore, it is known that soluble silico fluoric-compounds are converted gradually by alkalineearths into fiuorids and silicic acid. From the meager'information on the subject, itcannot. be determined whether this process is a complete one, but it seems not to be, inview of the fact that Reich, German Patent, 96,226, heats to incandescence the silico-fluoric salts-with lime to The produce a complete decomposition. transformation of the sodium silicofluorid lnto fluorid seems, therefore to have a limit also. This transformation does not transpire at a red heat or what are well known [with the production of fiuorids of the alkali and earth alkali metals. "found it is possible, by the'use of sodium as glow temperatures, but occurs at about 100 degrees C. and the reagents must be heated with water and in the finest imaginable comminution and be well mixed with each other. If there beadded the quantity of soda necessary for the formation of the sodium-aluminum fluorid, the product of the reaction consists of this double salt mixed with silicic acid and with only traces of sodium silico fluorid. A large number of chemical investigations has confirmed the fact that the double salt is really present and not only a mixture of aluminumfluorid or other aluminous fluorids and sodium fiuorid. The alumina necessary for this process is taken either from aluminum oxid, aluminum hydrate, alum'inate of soda, bauxite, clay, kaolin orany other suitablesource. The process is explained by the following equation;

Having thus described my invention, what I claim is:

1. The process of making sodium-aluminum fluorid which consists in mixing together sodium-silico-fluorid and alumina in a very finely divided state with water and heating them at approximately 1.00? C with the addition of the required quantity of sodium carbonate necessary for the formation of the double salt in stoechiemetrical .proportion.

2. The process of making sodium-aluminum fiuorid which consists in mixing together pulverulent sodium-silico-fiuorid 400 kg., pulverulent anhydrous alumina 108.5 kg, soda 113 kg. with Water, and at a temperature of about 100 C.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

EMIL TEISLER. Witnessesz PAUL ARRAs, ULYssEs J. BYWATER. 

